700R4 - essential to buy a newer case?

[6.5TDTahoe]

Requires 2WD out put shaft & extension housing!

[Robyn]

That is correct.

The case is the same but, the output shaft and tail housing must come from a 2 wheel drive application.

Pretty much the same rule applies to the TH 400, the TH 350 and the 4L80.

Robyn

[tomtaylor]

Hey Robyn, or anyone that would like to comment,

I have picked up 700R4/208 package from a 90 suburban 350 4x4. I was told by a trans shop that I would need 2 things for my rebuild. 1st was the computer from the suburban becuase it was controled by that. 2nd was that I would need a new stator for the 13 v-pump? So I have been reading alot about building these things on several sites and I found that Bowtie Overdrives offers a wiring kit for the 4 pin plug/solenoid and pressure switch inside the trans for the lockup that includes towing circuit/switch. Bowtie states that you absolutely do not need a computer to operate one of these trans.

Wherever I read I seem to get different detailed descriptions of little things to do to make this 700 work reliably. I am putting it behind my 6.2 so I don't need a monster I just need reliable and I would like to be able to tow without worrying about it. Have read about lots of people online here that had them well built and had no problems even when towing. Would love to hear anyones opinion about the best thing and the worst thing to do with these. Does everyone use 1200 stall converter on these?

Thanks for any detailed thoughts you all have.

[DmaxMaverick]

You do not need a computer to control the 700. It wouldn't know what to do with it. On emission controlled vehicles, the vehicle's computer ONLY controlled TCC (torque converter control), which is only an on/off function. This can be easily configured for automatic or auto/manual function.

You will not need the updated pump. The 1990 model should already have it. You will need the Diesel spec governor. You should use the low stall TC, but it is not absolutely necessary. I recommend it, but I know of a bunch of them that are using a gasser TC. With the higher stall converter, you will give up a lot of the low RPM torque, economy will suffer a little (all that fuel to wind it up is not needed to get going), your "effective operating range" will be reduced, as the redline on the Diesel comes in a lot quicker, and if towing, it will generate a lot more heat at lower speeds. If all you are using it for is a high-geared grocery-getter, the gasser TC may be fine.

The Trans-Go shift kit is HIGHLY recommended, as a starting point. If you have the thing scattered on the bench, you might as well add in some other "near bullet proof" hard parts. Otherwise, drive it sanely and save up or collect the parts along the way. Don't be fooled by the "I'm only running it behind a 6.2L so I don't need much" idea. Many times more 700's have been killed behind a 6.2L Diesel than much higher production, high-performance SBC's.

[tomtaylor]

You will not need the updated pump. The 1990 model should already have it.

Hi thanks for the info, since my trans is 21+ years old and and unknown history and miles shouldn't I just replace the pump with the rebuild? Or can it be tested it to see if it's good as is?

[DmaxMaverick]

The pumps were never a "problem", and rarely fail on their own. The later pump inserts (the "vanes" part) are only higher volume. You cannot "test" the pump independently, as they are integrated. They work, or they don't, with not much of anything in between. The 1990 700R4 was as good as they got, from production. The only place to go is into aftermarket hard parts, and the Trans-Go shift kit. The shift kit can be installed easily (valve body removal), but the hard parts require disassembly. If the tranny is otherwise healthy, I'd suggest only the shift kit, for now. Once installed and properly adjusted, you'll know what more may be needed. Unfortunately, that's the only way to know, short of complete disassembly.

[Robyn]

As maverick mentioned, the computer only controls the ON OFF function of the TCC

Now, this said the fellow at the tranny shop is partially correct. The late 700's (after about 88) do not have hydraulic shift valves for the TCC in the Valve body and they do the entire operation of the TCC with a solenoid valve run by the computer.

The earlier Valve bodies have actual valves in the VB that do the work and the solenoid was the final link to engage or disengage the TCC.

The 1990 model should have the valve bores in the VB and if so will accept the valve assemblies. (The bores have aluminum plugs that can be replaced with the valves)

If the VB does not have the bores, simply replace the VB with an 87 model that does have the bores

Transgo makes a great kit (700LU) or something like that to run the TCC totally with hydraulics and it can be tailored to lock up at the desired speed. NO WIRES. Its a great KIT

The governor must be used for the diesel (lower RPM shift speeds)

The pump changes were to increase oil flow volume.

The early pumps were also somewhat noisy.

Oil flow was the big issue though.

The other biggy is to get the Sun shell upgrade (Its called "The Beast")
The 2-4 band is also a needed upgrade (HD or better) they make kevlar, which is really good.

The 2-4 servo needs attention too. The 3-4 clutch pack must be upgraded with more clutches.

Upgrade the front sprag and the rear roller lock. (They are small and can break)

The little 6.2 will literally shake these things apart, so dont think, as Maverick mentioned that "its just a 6.2" The little 350 MOUSE motors are real easy on a tranny in comparison.

Have fun and good luck.

Missy